Anytime I use resources either single or multiple, the appointments does not display in the Horizontal Orientation at all (Day, Month, Week) except in Agenda but it does display in Vertical Orientation except in Month View.

In your code example, resource id is given is declared as string type but in appointment collection int value is assigned to OwnerId field which is the case for the issue. Kindly use resource id field as int type in both resource and appointment collection as shown below. We have prepared the sample for your reference which can be download from the below location.